The present invention relates to devices for displaying specimens for examination under magnification in general, and more particularly to such devices for counting, manipulation, and making viability assessment of cells.
With an increasing demand for quality agricultural products in an increasingly competitive agricultural market, animal artificial insemination (AI) techniques are becoming widespread as an effective means to achieve improved quality of stock, while at the same time reducing the costs and labor involved in natural breeding techniques.
AI techniques require the collection of semen from a producing male animal, and insemination of the female animal at a later time, and usually at a location more or less remote from the collection site. A consequence is that the semen to be used may be subject to degradation or decay due to the effects of temperature, time, or stress of shipment and storage. It is therefore necessary to analyze the quantity and vigor of the sperm within a sample, in assessing the fertilizing qualities of a particular ejaculate at the producing end, as well as in some cases in the insemination end.
One test is to count the quantities of active or motile sperm within a given volume of semen. The counting is carried out under a microscope or through the use of a photometer or with a photometer, and only considers a very small subset of the entire sample. However, because the subject of the count is moving, the presence of boundaries on the counting area can disadvantageously complicate the counting procedure. If the counting area constrains the sample within boundaries, the presence of the boundaries can affect the accuracy of the counting procedure because of the effect the boundaries have on the distribution of the sperm within the sample area. Some sperm for example will concentrate adjacent to a boundary.
Certain cell counters, or haemocytometers, minimize boundaries by placing a single drop of liquid sample between two precision formed optical plates. These devices, however, are very costly, and hence must be sterilized and reused. Other, disposable devices employ a screen-printed layer to define channels between a slide and a cover. However, these devices usually rely exclusively on capillary action for loading, and must be handled carefully to avoid the introduction of air bubbles which would prevent the complete filling of the specimen chambers. Moreover, prior art devices often accommodate only a very small quantity of liquid, sometimes as little as 1.3 μl, which makes analyses which take more than a few minutes to conduct problematic, as the specimen can dry out. Especially, when in the case of sperm cells, the specimen is maintained above room temperature on a heated microscope stage.
In addition, conventional devices are not readily loaded while under observation, making comparative analyses of specimens before and after the addition of some substance difficult.
What is needed is a low-cost disposable device for presenting a thin layer of known thickness of a sample allowing repeatable and accurate visual measurements to be made on the sample.